We propose that in sickle cell anemic individuals,the interaction of abnormal hemoglobin (Hb) with the cytoplasmic surface of the red cell may be the primary causative factor in the formation of Irreversible Sickle Cells (ISCs) which initiate microvascular occlusion and vasooclusive crises. In support of such a hypothesis we propose to study the following STRUCTURAL (1-3) and FUNCTIONAL (4-6) aspects of Hb-membrane interactions: (1) Binding affinity (ka) and total number of binding sites (by Scatchard analysis), and binding kinetics (by florescent quenching of a membrane embedded probe) will be determined individually for oxy- and deoxy- Hbs, methemoglobins and separated alpha and beta chains of Hb isolated from normal (AA) and sickle (SS) blood, on AA and SS inside out erythrocyte membrane vesicles (IOVs) on a comparative basis. (2) The specific binding sites, protein(s) and/or lipid(s) for the various Hbs on IOVs will be characterized by chemical cross- linking and/or photoaffinity labelling followed by electrophoretic analysis. (3) The specific binding site(s) of native membrane bound Hb in ISC fraction will be identified by chemical cross-linking followed by electrophoresis and/or by selective elution by no-ionic detergents followed by electrophesis under non-denaturing and denaturing conditions. (4) The deformability of membrane in resealed "hybrid ghosts" (in which the desired Hb type will be introduced into AA or SS membrane type and vice versa will be determined by ectacytometry under both oxygenated and de-oxygenated conditions. These studies distinguish the contribution of Hb- membrane interaction per se from the inherent abnormalities observed in SS membranes toward the sickling process. (5) The effect of selective alteration in protein and lipid composition of the membrane on the Hb-induced resealing will be investigated further in AA and SS red cells. (6) The release of membrane bound glycolytic enzymes by various Hbs will be studied under oxygenated and deoxygenated conditions using a rapid lysis technique. We hope the information gathered by these studies will be helpful in understanding the sickling process; such as understanding is essential in designing a suitable drug or developing other therapeutic approaches to correct this congenital disorder.